The design of polymer-biomolecule hybrid biomaterials with precisely defined properties has been proven to be critical in many biological applications. Immobilization of monoclonal antibodies/peptides on polymeric particles allows for targeted drug delivery (B. A. Khaw, Encyclopedia of pharmaceutical Technology 1998:2733; F. Marcucci et al., Drug Discovery Today 2004, 9:219). Immobilization of peptides/proteins on polymeric surfaces is of great interest for the development of biosensors and medical materials (M. Tirrell et al., Surface Science 2000, 500:61), while the immobilization of enzymes on polymeric fibers enables the preparation of biocatalysts (P. Gemeiner, In Enzyme Engineering: Immobilized Biosystems 1992:167).
Since biomolecules are much more chemically sensitive than typical small organic molecules, the choice of methods for covalent bond formation between biomolecules and polymers is limited to those occurring under specific and sufficiently mild conditions, which usually include aqueous solutions with pH values between 6 and 8, temperatures less than 37° C., and the absence of any reagents which may induce denaturation of biomolecules (L. Nobs et al., Journal of Pharmaceutical Sciences 2004, 93:1980).
The immobilization of biomolecules by binding them covalently to pre-formed polymers is based on the reaction between the functional groups on biomolecules and polymers. There are various natural or synthetic polymers with functional groups that have been reported for this purpose (M. I. Shtilman, Immobilization on Polymers 1993:341). In most cases, carboxylic acid, amine, or thiol groups on biomolecules take part in the reactions with the involvement of cross-linkers (G. T. Hermanson, Bioconjugate Techniques 1996:137). Those traditional immobilization methods can be limited by the operational complexity of the reaction procedure, the involvement of organic solvent or offensive reagents, instability of the functional groups, possible side-reactions and low immobilization efficiency (V. P. Torchilin, Biochimica et Biophysica Acta 2001, 1511:397; T. M. Allen, Biochimica et Biophysica Acta 1995, 1237:99).
There is therefore a need for simple, clean, and highly efficient immobilization chemistries which are applicable to a broad class of biomolecules. The concept of “click chemistry” was first introduced in 2001 (H. C. Kolb et al., Angewandte Chemie International Edition 2001, 40:2005). Sharpless and co-workers have used the term to describe chemical reactions that occur rapidly and selectively, without prior activation, and with high atom economy. Prototypical “click” reactions include cycloadditions of unsaturated species (especially the [2+3] Huisgen addition of azides to alkynes); nucleophilic substitution chemistry; carbonyl chemistry of the “non-aldol” type; and additions of carbon-carbon multiple bonds, including Diels-Alder chemistry. These reactions are diverse in scope yet orthogonal in reactivity, give very high yields, produce only inoffensive byproducts or no byproducts, occur under simple reaction conditions, and use benign solvents (including water). The strategy has been successfully utilized for rapid synthesis of small molecule libraries and enzyme inhibitors (H. C. Kolb et al., Drug Discovery Today 2003, 8:1128).